Laser sources are frequently used to illuminate subjects of interest and laser energy reflected therefrom is received by imaging sensors which employ signal and image processing algorithms to identify targets or other features of interest found in an image recorded by a focal plane detector.
The efficiency and sensitivity of these signal and image processing algorithms are significantly dependent on the spatial characteristics of the laser source illuminating a subject of interest. Therefore, by controlling the spatial characteristics of the laser source illuminating the subject of interest, the efficiency and sensitivity of the imaging processing algorithms can be substantially improved. Using lens pairs for divergence control and four sets of 2-axis pointing mirrors, or four sets of Risley prism pairs (for pointing control) in order to independently steer each of the four different laser beams is well known. Each, of these lenses, mirrors and prisms generally require mechanical mounting hardware and electronic control systems to control the positioning of these devices. Thus, overall, these devices and systems are complex and a simpler design is needed.
Normally, the spatial profile of a beam from a conventional laser device is characterized by a Gaussian cross-section, However, for many applications a more favorable profile of a laser beam is a flat-top profile. In order to convert a perfect Gaussian profile into a perfect flat-top profile an optical system with considerable complexity is usually required.
A need therefore exists in the art for an optical system that can perform the laser beam split and recombine function with a minimum of optical components and less complexity. Moreover, because the distance from the laser source to the target of interest may be variable, a need also exists for a system to adjust the divergence of the laser source, and the relative overlap of the laser beams as they are emitted from an illumination system to provide a beam with a flat-top profile.